Jewelry rings have traditionally been made by an "investment casting" process, such as, e.g., the process described in U.S. Pat. Nos. 5,136,858, 4,744,274, 4,626,145, 3,991,809, 3,735,800, and the like. In this process, a master ring is made by hand and thereafter encased in raw rubber, which is then heated and pressure cured to form a solid rubber block. The cured rubber block is then cut open, the master ring is removed, and the cavity within the rubber block is then filled with molten wax. After cooling, the wax ring thus formed is then removed from the rubber block and encased in "investment" (which is primarily "plaster of Paris). The investment is then heated to remove the wax encased therein and cooled to the desired casting temperature. Molten metal is then poured into the investment, the investment is allowed to cool, and then the investment is broken up (usually with a waterjet) to remove the cast ring.
In one embodiment of this process, a strip of silver with Roman numerals stamped into it is wrapped around the cast ring and inlayed into a groove around the outside of the ring. One example of the ring made via this embodiment is a Roman numeral ring, which is sold by Tiffany and Company and has met with a substantial amount of commercial success.
The process of making the Roman numeral ring, described above, is tedious and cumbersome. Furthermore, the ring made by the process often contains a substantial number of pits and has one or more surfaces which are not suitably smooth. At least one of these defects is due to the presence of "shrinkage porosity" within the cast ring.
During the investment casting process, when the metal in the investment changes for a liquid to a solid, it shrinks by about ten percent. This reduction in volume causes small voids in the cast product; and, after the cast ring is given a high polish by conventional means, this "shrinkage porosity" manifests itself as small pits in the highly polished ring surfaces.
It is an object of this invention to provide a process for preparing a silver ring with no "shrinkage porosity" and the appearance defects associated therewith.
It is another object of this invention to provide a process for preparing a silver ring with smooth surfaces.
It is yet another object of this invention to provide a process for preparing a Roman numeral silver ring with high definition recesses disposed on the top surface of the ring.